Automatic control for electric steam boilers



Jan. 7, 1 930. I M sc ml 1,742,406

AUTOMATIC CONTROL FOR ELECTRIC sums BOILERS Filed Jan. 29, 192'! m/vz/vroe G/m/A/y/v/ AscAE/N/ B) s I arrog/vsy Patented Jan. 7, 1930 UNITEDSTATES GIOVANNI MASGARINI, F MILAN, ITALY -AUTOMATIC CONTROL FORELECTRIC STEAM BOILERS Application filed January 29, 1927, Serial No.164,637, and in Italy February 25, 1926.

The present invention has for its subject matter an electromagneticrelay closing and opening an electric circuit for two values of anelectric current to be controlled lying in close vicinity to oneanother.

The fi ure attached illustrates the principle on w ich the invention isfounded as well as one of the various practicable execution forms forcarrying such a principle into effect.

With reference to the figure, 1 is a coil having inside a stationaryiron core 2 and a travelhng iron core 3. "When the travelling core 3 isnot sucked in, it rests on one arm of a two armed lever 4 swinging aboutthe pivot 5, whose other arm carries a contact element 9, whereas at theopposite lever end asliding counterweight 11 is fitted. The length ofthe two lever arms is so proportioned that the couple due to the contact9 is somewhat in excess of the couple due to the counterweight 11.

Across the ends of the coil 1 a secondcoil 12 is connected, a travellingiron core 13 be- 2 in arranged inside of this second coil.

The set comprising the two coils and eventually an amperemeter 14 istraversed by the current to be controlled or by a current proortional tothe said current and'supiplied, so or instance, by a transformer 15provi ed on the line 16. r

The contacts 9-10 close and open an auxiliary circuit 19 which mayeventually be supplied with current from a transformer 17 at a 85suitable pressure. a

1 The working of the arrangement is as folows:

When the current traversin the coil 1 has attained a predetermined v uede ending 40 from the characteristics of said coil, t e travelling core3 is sucked in and comes into contact with the stationary core 2. Thelever 4:, being now released from the weight of the core 3, will swingabout its pivot 5 and close the auxiliary circuit 19 at 9-10, thusactuat-.

.ing the signalling and automatic adjustment devices.

When due to the eflected adjustment or through any other cause whateverthe ourrent sinks to a certain value below its, previ-- ous value,the-travelling core3 detaches itself from the stationary core 2 andweighting down the lever 4 will cause the lever to swing in oppositedirection to the previousone so as to open the auxiliary circuit 19 at9-10.

The degree of sensitiveness of the relay, that is to say the differencebetween the two current values for which the suction and release of thetravelling core take place, varies with the length of the core strokeand can be 60 set to any desired value by means of the regulating screw6, this screw acting on the lever i to the effect of limit the amplitudeof its swinging and therewith the downward stroke of the core 3. v

The adjustable screw 7 is intended to suitably limit the oscillations ofthe lever 4 to the eli'ect of allowing it to close the contacts 9-10 butat the same time preventing it from following the travelling core 3through the whole upward stroke. In this manner an interstice will beleft between the upward moving core 3 and the lever 4, so that the corevibrations will be prevented from transmitting themselves to the lever4. and contacts 7 9-10, such vibrations being obviously noxious.

When the set comprising the coil 1, cores 2 and 3 and adjustable screws6 and 7 has been established in its various elements, the sucso tion andrelease of the core 3, and consequently the closing and opening of theauxiliary circuit 19 at 9-10, will take place for two predeterminedvalues of the current to be controlled.

In order to enable the apparatus to operate for diiferent values of thecurrent to be con trolled, the coil 12 shunted on the coil 1 isprovided. As the current traversing the apparatus divides itself overthe two coils in reverse ratio to their apparent resistances, b varyingthe reactance of the coil 12 through displacement of its core 13, thecurrent flow mg through the coil 1 can be caused to remain steady on itsnormal working value, that is i to say the relay can be made to operatefor different values of the current to be controlled, these values beincomprised between two limits depending rom the electric and magneticcharacteristics of the two coils.

1 range, a transformer 15 with two or more carrying the tice; it will beclear that the form, arrangedegrees of sensitiveness,viz.,with two ormore transformation ratios, may be provided, the apparatus beinginserted on one or the other 0 the diflerent circuits by means of achangev over switch 18.

The coil 12 fitted with travelling iron core may be replaced by asuitably adjustable ohmic or mixed (ohmic and inductive) resistance; theeffect would be the same.

The drawin relates to one mode only of evised apparatus into pracmentand method of grouping the various parts may be altered to suit thedifferent cases.

In the description we have spoken only of the current control. It willbe readily understood, however, that the adoption ofwattmetric andpressure windings would permit the control of the effective load on aline or of the otential difference between two points.

T e apparatus as described is especially adapted to the control ofelectric steam boilers of the electrode type. In the drawing, anelectric steam boiler 20 has electrodes 21 contained therein, theseelectrodes are each connected to the mains 16.. Said boiler hasconnected thereto a pipe 22 for feeding or discharging water from theboiler depending upon the conditions existing in auxiliary circuit 19..Said pipe 22 is connected to a feed water pipe 23 through which water isforced into boiler 20 by means of pump 24. Pipe 22 is also connected toan electrically operated valve 25, which controls the discharge of waterfrom the boiler through the discharge pipe 26 and which is adapted to beelectrically connected to auxiliary circuit 19. Valve 26 is normallyclosed and is opened only when auxiliary circuit 19 is energized.

The operation of this control system is such that when the water in theboiler'reaches a certain predetermined level a predetermined load isplaced on the mains 16. When sulficient power passes through the coil 'lthe movable core 3 is lifted thereby causing lever 4 to swing in aclockwise direction and close contacts 9 and 10. The auxiliary circuitand valve 25 will be energized or deenergize'd depending on the desiredelectrical load on the boiler. Since a water level in the boiler higherthan that which has been predetermined will result in a greater wettedelectrode surjustment of the traveling core 13 when it is desired tomaintain a different load on the boiler.

In the case of electric steam boilers, when the adjustment is carriedout through operation of movable elements, the auxiliary c1rcuit 19 maybe caused to operate an electric motor or any other device manipulatingthe said movable elements.

The apparatus according to the invention may be inserted, eitherdirectly or throu h the intermediary of a transformer, on t e feed lineof an electric current distribution system, and may be used to vary theload or the current absorbed by the boiler in such a manner as tomaintain constant the load or current respectively of the'general line,in other words, in such a manner as to cause the boiler to absorb allthe load or current respectively that at any given moment remains.available.

- I declare that what I claim is :-v

1. Appliance for the regulation of water admission and water level inelectricallyheated boilers furnished with electrodes, for the purpose ofregulating and limiting the current intake rate of the boiler,characterized in that the current to be regulated excites two solenoidsconnected in parallel re{ lation to each other, of which one has a fixedcore and a movable core which in a demagnetiz'ed condition is supportedon a lever arm and maintains an auxiliary electrical circuit open whilein the magnetized condition it frees the lever through whose turnin thecircuit is closed, the second solenoid eing an I inductive resistancewith movable iron core, through whose movement, owin to change incurrent distribution between t e two solenoids, the magnetic eflt'ect ofthe first solenoid is adjustable to diflerentvalues of th current to beregulated.

2. Device according to claim 1 wherein on closing the auxiliary circuit,a current 0 ens a valve provided on the feed ipe of the oiler so thatthe water supplie by the feeding device and, if necessary also a art ofthe water present in the boiler isle away, and by dis lacement of thecore of the second solenoi the level of the water resent in the boileris limited to a value whic corres onds to the current consumption forwhich t e device is calibrated, whlle on opening the secondary circuit,the valve is closed and makes.

possible the feedin of the boiler.

3.Device according to claim 1 characterized in that a screw, a ainstwhich the lever influenced by the weig t of the movable core rests,permits the regulation of the throw of.

the lever and thereby the stroke of the core 7 and the sensitivity ofthe device.

4. Device according to claim 1 character ized in that a screw limits themovement of the lever influenced by the weight of the movable core insuch a way that the lever is so far released from the completelyaspiratedeore that the latter cannot transmit the oscillations producedby the alternating current to the former.

(Italy), this 13th day of Signed at Milan J an., 1927.

GIOVANNI MASCARINI.

